According to Wideband Code Division Multiplex Access (W-CDMA), which is a mobile telecommunications interface specified by 3GPP (3rd Generation Partnership Project) that is one of the International Standards Groups, upstream channels such as a DCH (Dedicated Channel) and an E-DCH (Enhanced DCH) are defined. A plurality of data series transmitted while being carried on one of these channels is present (data series 1, 2, . . . and N). Data pieces at appropriate data lengths are clipped from the data series, respectively and the clipped data pieces are combined, thereby forming transmit data. A combination of the lengths of the data pieces clipped from the respective data series is referred to as “TFC”.
Several tens to several hundreds of TFCs are present. A set of TFCs that are possibly present is referred to as TFCS (Transport Format Combination Set). FIG. 7 shows examples of the TFCS and TFC. “TABLE” shown in FIG. 7 is an example, of the TFC for which the number N of columns of data series is 2 (N=2) (data series-1 and -2) and the number of TFCs is 9 (TFC(1)-(9)).
Generally, higher total transmit power is required for mobile communication as transmit data is larger in size. Conversely, lower total transmit power is required for mobile communication as transmit data is smaller in size. Thus, the total transmission power differs among the TFCs.
Meanwhile, transmission process in the DCH or E-DCH is implemented according to a procedure 300 shown in FIG. 5. First, a TFC decision unit 301 decides a TFC which can be transmitted with a total transmit power that does not exceed a maximum value of allowable transmit power. A transmit data creation unit 302 clips data pieces from data series 1, 2, . . . and N, respectively, and combines the clipped data pieces based on each of the TFC decided by the TFC decision unit 301, thereby creating transmit data. A transmit data process unit 303 implements error correcting coding and interleaving on the created transmit data. Finally, a frequency conversion unit 304 modulates the transmit data processed by the transmit data process unit 303 and outputs the modulated transmit data as a carrier.
In a series of the foregoing units, the TFC decision unit 301 includes functions shown in FIG. 6. A total transmit power calculation unit 401 calculates total transmit powers of each TFC in a TFCS. A TFC selection unit 402 selects a TFC having a highest total transmit power from among the TFCs the total transmit powers of which do not exceed the maximum value of allowable transmit power.
As to selection of a TFC, there is known a technique as disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-304195. This document discloses a TFC selection method for a mobile terminal device selecting a TFC that specifies a combination of transmit data lengths at predetermined time intervals in each transport channel, multiplexing transmit data on respective transport channels based on the selected TFC and transmitting the multiplexed transmit data.